When is a pre-approval necessary?

Most of the people are confused whether a mortgage pre-approval is necessary to make an offer on a house. I would like to make it clear, a pre-approval is not always a compulsory process. But, we should note, basically, a mortgage pre-approval letter is a guarantee from a lender that it's willing to finance your home purchase up to a certain dollar amount. So, here lies the importance of the process.

The situations in which a pre-approval letter is not necessary are:
1. If you are paying the hard cash so that you don't need a loan
2. If you are an ideal home-buyer(You are having a stable job and a fair credit history.)

Certain situations in which you need a pre-approval:
1. You are less than an ideal home buyer
2. You are in a hot market
3. You are not sure how much house you can afford.